Dynamic paint erase paint doesnt work?
On the Canvas there should be Dynamic Paint Advanced options. This includes 'Dry' and 'Dissolve' settings. The 'Dry' allows your 'wetmap' to dry over time whereas the 'Dissolve' setting allows your paint to revert back to its initial colour over a series of framee - in my experience you should only enable one of these two options as the 'Dry' seems to disable 'Dissolve'.

Enable 'Dissolve' and set the number of frames to the number of frames you want the paint to remain - if you want it to instantly revert then set it to '1' and uncheck 'Slow'.



This should produce something like the following :



Note also that the dynamic paint treats timeline frame 1 as a special case where the paint is automatically reset and rendered. If you are on a different frame the dynamic paint will not automatically update in the viewport.